Bi-Directional Electric Energy Meter

ABSTRACT

An electric energy meter for a poly-phase electricity network includes a power transformer having a primary side and a secondary side, a first analog front end (AFE) unit is coupled to the secondary side of the power transformer, and a microcontroller coupled to the primary side of the power transformer. The first AFE unit is to be coupled to a first phase of the poly-phase electricity network. The microcontroller is configured to transmit a digitized request signal to, and to receive a measurement signal from, the first AFE unit via the power transformer. More specifically, the first AFE unit, upon receiving the digitized request signal, is to extract information from the digitized request signal.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This continuation application claims priority to U.S. patent applicationSer. No. 14/698,586, filed Apr. 28, 2015, which is a continuation ofcopending International Application No. PCT/CN2014/094962, with aninternational filing date of Dec. 25, 2014, which designated the UnitedStates, both applications of which are hereby fully incorporated hereinby reference for all purposes.

BACKGROUND

An electric energy meter is used to measure how much electrical energy aload has consumed from a source. Generally, the electric energy meter iscoupled to an electricity network that connects between the load andsource.

SUMMARY

Systems and methods to measure electric energy using the inventedelectric energy meter are disclosed herein. In an embodiment, anelectric energy meter for a poly-phase electricity network includes apower transformer having a primary side and a secondary side, a firstanalog front end (AFE) unit is coupled to the secondary side of thepower transformer, and a microcontroller coupled to the primary side ofthe power transformer. The first AFE unit is to be coupled to a firstphase of the poly-phase electricity network. The microcontroller isconfigured to transmit a digitized request signal to, and to receive ameasurement signal from, the first AFE unit via the power transformer.More specifically, the first AFE unit, upon receiving the digitizedrequest signal, is to extract information from the digitized requestsignal.

In another embodiment, an apparatus for a poly-phase electricity networkincludes a power transformer having a primary side and a secondary side,a first plurality of analog front end (AFE) units coupled to thesecondary side of the power transformer, a second plurality of AFE unitscoupled to the secondary side of the power transformer, and amicrocontroller coupled to the primary side of the power transformer.More specifically, each of the first plurality of AFE units is to becoupled to a separate phase of the poly-phase electrical distributionand configured to measure current for that particular phase. Each of thesecond AFE units is to be coupled to a separate phase of the poly-phaseelectricity network and configured to measure voltage for thatparticular phase. The microcontroller is configured to transmit adigitized request signal to each of the first and second AFE units andto receive measurement data from the first and second AFE units via thepower transformer. One of the first plurality of AFE units and one ofthe second plurality of AFE units are to be coupled to each phase.

Yet in another embodiment, a method includes transmitting, by amicrocontroller coupled to a primary side of a power transformer, adigitized request signal to a plurality of analog front end (AFE) units,wherein each AFE unit is coupled between a secondary side of the powertransformer and one phase of poly-phase electricity network, uponreceiving the digitized request signal, activating the plurality of AFEunits, measuring, by a first AFE unit, a first phase of current of apoly-phase electrical distribution, measuring, by a second AFE unit, thefirst phase of voltage of the poly-phase electrical distribution, andtransmitting, by the first and second AFE units, the measured currentand voltage for the first phase of the poly-phase electricaldistribution to the microcontroller.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments of the invention,reference will now be made to the accompanying drawings in which:

FIG. 1 shows a block diagram to illustrate an electric energy metercoupled to a poly-phase electricity network in accordance with variousembodiments;

FIG. 2 shows an example to further illustrate an analog front end (AFE)unit in accordance with various embodiments;

FIG. 3 shows an example to illustrate an electric energy meter coupledto a single-phase electricity network in accordance with variousembodiments; and

FIG. 4 shows a flow chart illustrating a method to measure electricenergy using the disclosed electric energy meter in accordance withvarious embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, companies may refer to a component by different names. Thisdocument does not intend to distinguish between components that differin name but not function. In the following discussion and in the claims,the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . ” Also, the term “couple” or “couples” is intended tomean either an indirect or direct connection. Thus, if a first devicecouples to a second device, that connection may be through a directconnection, or through an indirect connection via other devices andconnections.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of theinvention. Although one or more of these embodiments may be preferred,the embodiments disclosed should not be interpreted, or otherwise used,as limiting the scope of the disclosure, including the claims. Inaddition, one skilled in the art will understand that the followingdescription has broad application, and the discussion of any embodimentis meant only to be exemplary of that embodiment, and not intended tointimate that the scope of the disclosure, including the claims, islimited to that embodiment.

Electric energy meters receive current and voltage input signals fromthe electricity network. In a typical poly-phase (e.g., three-phase)electric energy meter, current input signals for the three phases comefrom a three-phase electricity network via current transformers andvoltage input signals come from the three phases of the electricitynetwork via resistive voltage dividers. The current and voltage inputsignals are sampled by the meter and the current samples are multipliedwith the voltage samples to obtain electric power samples. Accumulatingthese energy samples over time provides an indication of consumedelectric power (energy).

Further, some electric energy meters convert the current and voltageinput signals to digital input samples for further processing by amicrocontroller. Generally, separate input channels in the meter areused for each of the three current and voltage input signals, and eachinput channel includes its own analog front end (AFE) unit, currenttransformer and/or a voltage divider. This approach is generallyreferred to as a synchronous approach since all input signals areprocessed in parallel and synchronously. With this approach, each AFEunit for each input channel is coupled to the electricity network via adedicated current transformer (in the case of AFEs receiving currentinputs) to avoid a mismatch issue. The AFE units are typicallyintegrated with the microcontroller meaning that the microcontroller mayhave dedicated inputs for each of the AFE units. The dedicated AFE unitsand current transformers may cause an increased complexity to design themicrocontroller, and may in turn possess a large die size. Since the diesize may be a premium, such an approach may disadvantageously increasethe cost of production.

The disclosed embodiments are directed to an electric energy meter thateliminates the requirement to integrate AFE units with amicrocontroller. The microcontroller of the disclosed meter communicateswith the AFE units via a communication medium and thus each of themicrocontrollers and AFE units have individual connections to thecommunication medium. As such, the microcontroller does not haveseparate connections to each of the various AFE units. In the exampledisclosed herein, the communication medium is a single transformer.Implementing the disclosed meter to measure electric energy mayadvantageously provide a less complex design of the microcontroller andthus reduce the cost.

The disclosed electric energy meter may not be limited to be used for apoly-phase electricity network. In accordance with various embodiments,the meter may also be used in a single-phase electricity network.

FIG. 1 shows a block diagram 100 to illustrate a three-phase electricenergy meter 180 in accordance with various embodiments. Theillustrative electric energy meter 180 is connected to three phases A,B, C of a three-phase power source 122 which feeds a three-phase load120. As noted above, although the disclosed electric energy meter 180shown in FIG. 1 is a three-phase electric energy meter, the disclosedelectric energy meter 180 may be connected to a poly-phase electricitynetwork or a single-phase electricity network. For clarity, thefollowing discussion will be limited to implement the electric energymeter 180 for three-phase electricity network. However, for the electricenergy meter connected to a single-phase electricity network, theoperation principle will be separately provided with respect to theblock diagram of FIG. 3.

Still referring to FIG. 1, the illustrative electric energy meter 180further includes a microcontroller unit (MCU) 102, a transformer 104,six AFE units 106, 108, 110, 112, 114, and 116. In accordance withillustrative embodiments, the transformer 104 includes primary (P) andsecondary (S) sides. The MCU 102 connects to the primary side and theAFE units 106, 108, 110, 112, 114, and 116 connect to the secondaryside.

Since the electric energy meter 180 is configured to measure theelectric energy with three phases A, B, and C, in an embodiment, eachphase includes a current signal and a voltage signal. For example, phaseA includes a current signal I_(A), phase B includes a current signalI_(B), and phase C includes a current signal I_(C). Further, the currentand voltage signals at each phase are coupled to the AFE units via aresistive element (e.g., 136, 138, and 140) and a voltage divider (e.g.,V_(DA), V_(DB), and V_(DC)) respectively. More specifically, the currentsignal I_(A), corresponding to the phase A, is converted to a voltagesignal V_(IA) via the resistive element 136, and the voltage signal isreceived by the AFE unit 106. The current signal I_(B), corresponding tothe phase B, is converted to a voltage signal V_(IB) via the resistiveelement 138, and the voltage signal is received by the AFE unit 108. Thecurrent signal I_(C), corresponding to the phase C, is converted to avoltage signal V_(IC) via the resistive element 140, and the voltagesignal is received by the AFE unit 110. Still more specifically, via thevoltage divider, the voltage signal at each phase is converted to avoltage (e.g., V_(A), V_(B), and V_(C)) that the corresponding AFE unitis configured to receive. For example, the AFE unit 112 is configured toreceive V_(A) that corresponds to the phase A via the voltage dividerV_(DA). The AFE unit 114 is configured to receive V_(B) that correspondsto the phase B via the voltage divider V_(DB). The AFE unit 116 isconfigured to receive V_(C) that corresponds to the phase C via thevoltage divider V_(DC).

Continuing in FIG. 1, in accordance with various embodiments, thetransformer 104 is a digital transformer that is configured to transmitdigital signals between the primary and secondary sides of thetransformer. Moreover, the transformer 104 is preferably to beimplemented as a circuit integrated on a printed circuit board (PCB).

FIG. 2 shows an example to further illustrate the AFE unit 106 inaccordance with various embodiments. The other AFE units of FIG. 1 mayshare the same architecture and operating principle as AFE unit 106. Asshown in FIG. 2, the AFE unit 106 further includes ananalog-digital-conversion (ADC) unit 202, a recovery circuit 204, and atransceiver 206.

More specifically, the ADC unit 202 is coupled to the electricitynetwork and configured to digitize the input voltage (V_(IA)). Thetransceiver 206 is coupled to the secondary side of the transformer 104and is configured to receive/transmit signals to and from the MCU 102through transformer 104. The recovery circuit 204 coupled to thetransceiver 206 is configured to recover the signal received by thetransceiver 206. Further, the recovery circuit 204 extracts informationsuch as clock and data information from the recovered signal.

Generally, the clock information is used to synchronize each AFE unit.In some embodiments, the extracted data may include executedinstructions. Such executed instructions, together with the clockinformation, may be used by the MCU 102 to specify which AFE unit is toretrieve current or voltage signals from the electricity network andwhich AFE unit is operable to transmit digitized current or voltagesignals back to the MCU 102.

For example, based on the extracted clock and data information(extracted by the recovery circuit 204), the AFE unit 106 is assigned bythe MCU 102 to retrieve V_(IA) and digitize the retrieved V_(IA) duringa first minute. During a subsequent minute, the AFE unit 106 may beassigned by the MCU 102 to transmit the digitized V_(IA) (by thetransceiver 206) to the MCU 102 via the transformer 104. In accordancewith illustrative embodiments, each of the AFE units 106, 108, 110, 112,114, and 116 is operable either to retrieve and digitize current orvoltage signals or to transmit the digitized signals via the transformer104 to the MCU 102. Through the transformer 104, the MCU 102 cansequentially communicate with each AFE unit 106-116. Further details ofthe operation of the electric energy meter 180 will be discussed withrespect to the flow chart in FIG. 4.

FIG. 3 shows an alternative example to illustrate an electric energymeter 300 to be coupled to a single-phase electricity network. In FIG.3, the electric energy meter 300 is connected to the single-phaseelectricity network in which a source 301 feeds power to a load 303 viaa single-phase line 333 and a neutral line 335.

The electric energy meter 300 is configured to estimate the single-phaseelectric energy consumption by measuring current signals flowing throughthe lines 333 and 335. The current signal flowing through the line 333is I_(sp); the current signal flowing through the neutral line isI_(neutral). More specifically, the electric energy meter 300 receivesmeasured voltage signals, V_(sp) and V_(neutral), which are converted,by the resistive element 313 and 315 respectively, from the currentsignals I_(sp) and I_(neutral).

Still referring to FIG. 3, the electric energy meter 300 is implementedwith an architecture that is similar to that of the electric energymeter 180 of FIG. 1. As shown in FIG. 3, the electric energy meter 300includes the MCU 102, the transformer 104, and AFE units 302 and 304. Insome illustrative embodiments, the AFE units 302 and 304 are connectedthe secondary side of the transformer 104, and the MCU 102 is connectedto the primary side of the transformer 104.

The AFE unit 302 is configured to receive the converted voltage signalV_(sp) (which represents current I_(sp)) and further digitizes thereceived voltage signals V_(sp). The AFE unit 304 is configured toreceive the converted voltage signals V_(neutral) (representingI_(neutral)) and further digitizes the received voltage signalsV_(neutral). For a purpose of clear illustration, only the AFE units(i.e., 302 and 304) configured to receive the converted current signals(i.e., I_(sp) and I_(neutral)) are shown. That is, other AFE units maybe included in meter 300 but may be unused.

In accordance with various embodiments, the operation of the electricenergy meter 300 is similar to the one of the electric energy meter 180.The MCU 102 starts to transmit a digitized request signal to the AFEunits via the transformer 104.

FIG. 4 shows a flow chart for a method 400 using the disclosed electricenergy meter to measure electric energy in accordance with variousembodiments. The operations may be performed in the order shown, or in adifferent order. Further, two or more of the operations may be performedin parallel instead of sequentially.

The method 400 starts in block 402 by transmitting, by the MCU 102, adigitized request signal to one of the AFE units. In accordance withillustrative embodiments, the digitized request signal transmitted viathe transformer 104 includes power, and information of data and clock.As mentioned above, the information may include a variety ofinstructions for the AFE unit to execute and the information of clock isoperable to synchronize the AFE unit with the MCU 102.

After the AFE unit receives the request signal, the method continues inblock 404 with activating the AFE unit. More specifically, once the AFEunit receives the request signal, the AFE unit is activated by the powerof the request signal. The activated AFE unit is configured to recoverthe request signal so as to extract the information of data and clock.Preferably, the recovery and extraction is performed by the recoverycircuit (e.g., 204) of the AFE unit.

Still referring to FIG. 4, after the AFE unit extracts the informationof data and clock, the AFE unit is synchronized with the MCU 102 basedon the extracted information of clock. Further, the AFE unit isconfigured to execute the extracted information of data (instructions).Executing the instruction leads the method 400 to block 406 in whichcurrent signals for a first phase are measured. Subsequently, the MCU102 may transmit another digitized request signal to another AFE unit toactivate the AFE unit. Then the method 400 continues at block 408 withmeasuring voltage signals for the first phase. More specifically, themeasurement of voltage and current signals are performed by the AFEunits to receive converted voltage signals (e.g., V_(IA), V_(IB),V_(IC), V_(A), V_(B), and V_(C)) from the electricity network.

For example, the MCU 102 transmits a first digitized request signal tothe AFE unit 106 via the transformer 104. The AFE unit 106 receives anddecodes and extracts the instruction from the first digitized requestsignal. The AFE unit 106 AFE unit 106 then begins to receive V_(IA) forthe phase A of the electricity network. Subsequent to the MCU 102transmitting the first digitized request signal, the MCU 102 maytransmit a second digitized request signal to the AFE unit 112.Analogously, the AFE unit 112 is configured to start to receive V_(A)from the electricity network.

After the AFE units receives converted voltage signals (e.g., V_(IA) andV_(A)) from the electricity network in block 406 and 408, the method 400continues at block 410 with digitizing the voltage signals. In someembodiments, the ADC unit of each AFE unit is configured to digitize thereceived voltage signals. For example, the ADC unit 202 of the AFE unit106 digitizes the received voltage signal V_(IA).

The method 400 continues in block 412 with transmitting a handshakesignal by the AFE unit to the MCU 102, and receiving an acknowledgementsignal by the AFE unit. More particularly, the handshake signal istransmitted from the AFE unit to the MCU 102 via the transformer 104. Inan example, the handshake signal may enable the MCU 102 to determinewhether the AFE unit that transmits the handshake signal has matchedinformation of clock. If the MCU 102 approves the handshake signal, theMCU 102 may transmit an acknowledgment signal to the AFE unit.

Still referring to FIG. 4, after the AFE unit receiving theacknowledgement signal, the method 400 continues at block 414 withtransmitting the digitized voltage signals to the MCU 102 via thetransformer 104. In some embodiments, the transceiver of each AFE unitis configured to transmit the digitized voltage signals. For example,the transceiver 206 of the AFE unit 106 transmits the digitized voltagesignal to the MCU 102 via the transformer 104.

After the MCU 102 receives the digitized voltage signals, the MCU 102 isconfigured to process the digitized voltage signals and estimate anamount of electric energy of the first phase that has been consumed bythe load 120.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. An electric energy meter for a poly-phaseelectricity network, comprising: a power transformer having a primaryside and a secondary side; a first analog front end (AFE) unit iscoupled to the secondary side of the power transformer and is to becoupled to a first phase of the poly-phase electricity network; and amicrocontroller coupled to the primary side of the power transformer,and configured to transmit a digitized request signal to, and to receivea measurement signal from, the first AFE unit via the power transformer;wherein the first AFE unit, upon receiving the digitized request signal,is to extract information from the digitized request signal.
 2. Theelectric energy meter of claim 1 wherein the digitized request signalincludes power, clock information, and data.
 3. The electric energymeter of claim 2 wherein the first AFE unit includes a recovery unitactivated by the power of the digitized request signal and configured toextract the information, wherein the extracted information includesclock information and data from the digitized request signal.
 4. Theelectric energy meter of claim 3 wherein the first AFE unit, based onthe extracted clock information and data, is to digitize a currentmeasurement and to transmit the digitized current measurement for thefirst phase to the microcontroller.
 5. The electric energy meter ofclaim 1 further comprising a second AFE unit to be coupled to the firstphase and configured to measure voltage for the first phase of thepoly-phase electrical distribution.
 6. The electric energy meter ofclaim 1 wherein the power transformer is included on a printed circuitboard.
 7. An apparatus for a poly-phase electricity network, comprising:a power transformer having a primary side and a secondary side; a firstplurality of analog front end (AFE) units coupled to the secondary sideof the power transformer, each of the first plurality of AFE units is tobe coupled to a separate phase of the poly-phase electrical distributionand configured to measure current for that particular phase; a secondplurality of AFE units coupled to the secondary side of the powertransformer, and each of the second AFE units is to be coupled to aseparate phase of the poly-phase electricity network and configured tomeasure voltage for that particular phase; and a microcontroller coupledto the primary side of the power transformer and configured to transmita digitized request signal to each of the first and second AFE units andto receive measurement data from the first and second AFE units via thepower transformer; wherein one of the first plurality of AFE units andone of the second plurality of AFE units are to be coupled to eachphase.
 8. The apparatus of claim 7 wherein the microcontroller isconfigured to transmit the digitized request signal respectively to oneof the first plurality of AFE units and one of the second plurality ofAFEs that are to be coupled to a common phase.
 9. The apparatus of claim8 wherein, upon an AFE unit receiving the digitized request signal, theAFE unit is to extract clock information and data from the digitizedrequest signal.
 10. The apparatus of claim 9 wherein each AFE unitfurther includes a recovery unit that is activated by power of thereceived digitized request signal, and the AFE unit, upon beingactivated by its recovery unit, is to extract the clock information anddata.
 11. The apparatus of claim 10 wherein, based on one of the AFEunits of the first plurality of AFE units extracting the clockinformation and data, such AFE unit is configured to digitize themeasured current for the phase to which that AFE unit is to be coupled,and the AFE unit of the second plurality of AFE units to be coupled tothe common phase is configured to digitize the measured voltage for thecommon phase.
 12. The apparatus of claim 7 wherein the power transformeris included on a printed circuit board.
 13. A method, comprising:transmitting, by a microcontroller coupled to a primary side of a powertransformer, a digitized request signal to a plurality of analog frontend (AFE) units, wherein each AFE unit is coupled between a secondaryside of the power transformer and one phase of poly-phase electricitynetwork; upon receiving the digitized request signal, activating theplurality of AFE units; measuring, by a first AFE unit, a first phase ofcurrent of a poly-phase electrical distribution; measuring, by a secondAFE unit, the first phase of voltage of the poly-phase electricaldistribution; and transmitting, by the first and second AFE units, themeasured current and voltage for the first phase of the poly-phaseelectrical distribution to the microcontroller.
 14. The method of claim13 further comprising digitizing, by the AFE units, the measured currentand voltage for the first phase before transmitting to themicrocontroller.
 15. The method of claim 14 further comprisingrecovering, by the microcontroller, the measured current and voltage forthe phase that are transmitted by the first and second AFE units.